In the past, as a semiconductor module which is used in vehicles, for example, a semiconductor module such as that described in Japanese Unexamined Patent Application Publication No. 2009-159815, in which a series circuit provided with an upper arm and a lower arm is built-in and a semiconductor element and a diode in the same arm overlap each other, has been known. Then, the semiconductor module is cooled by providing cooling metals on both sides of the module and providing a cooling channel which is folded back at the diode side.